Industry has long used various types of electrical wiring and interconnects. These frequently employ shielding which covers the individual wires. This shielding is intended to provide an electromagnetic barrier between the shielded wire and other wires or the electromagnetic environment. These shields cannot perform their intended function if they are not electrically teminated in a mechanically and electrically suitable manner.
Shielding a permanent section of line can be accomplished in a cost effective manner during the manufacturing operation. However, where connectors are concerned, it may be mechanically convenient to break the grounding shield to facilitate connection and reintroduce the shield on the other side of the connector. This produces a gap in the shields covering of the wire bundle, and thus degrades the ground shield's electrical effectiveness.
Presently, the wire grounding hardware will usually consist of grounding studs such as a screw, nut and washer, which must be mounted on an adequately conductive surface. The grounding wire is terminated in lugs with a round hole which must be placed over the ground stud screw and held in place using the nut and washer. Assembly requires larger working space and good dexterity. For reasons of mechanical access, the ground stud must usually be located a minimum of several inches from its associated electrical connector.
Other methods utilize a special back shell for the electrical connectors. These are an improvement on ground studs, but the method of mechanically terminating the wire or shield in these special back shells differs from the method used to terminate the wires at the connector. The use of the back shell requires special training and handling practices and procedures. Disassembly and reassembly of these grounded connections for repair or trouble shooting is very difficult.
Normally when the shield is interrupted, the ground shield is grounded to the support structure, which in aerospace applications is typically an airframe. The length of the connection from the ground shield interrupt to the airframe, also known as the pigtail, is an important consideration. Long pigtails and poorly chosen grounding points can seriously degrade the ground shielding to the point of negating the usefulness of the ground shield.